A lubricating structure of a valve-operating chain of a vertical engine mounted in an outboard engine unit is disclosed in Japanese Patent Laid-Open Publication No. 2004-346891 (JP 2004-346891 A).
A lubrication structure of a timing chain of an engine having a variable valve timing mechanism is disclosed in Japanese Patent Laid-Open Publication No. 2001-303919 (JP 2001-303919 A).
The lubrication structure disclosed in JP 2004-346891 A is structured to allow oil to flow down along ribs from the ceiling surface of a chain cover and to bring oil into contact with a timing chain. A camshaft-side oil jet is disposed in the oil supply channel.
However, considering the length of the main body portion of the oil jet, the oil supply channel must be disposed near upper cylinders, and a configuration is needed that has a higher degree of freedom of design. The jet nozzle sprays oil toward the meshing area of the chain. Therefore, a portion of the dispersed oil is captured and guided by the upper ribs to lubricate the chain again, and the rest of the oil is recovered. Efficiency is improved if the ratio of oil supplied for lubrication is increased.
The lubrication structure disclosed in JP 2001-303919 A is a structure, provided in an ordinary engine having variable valves rather than in a vertical engine, in which an oil channel is disposed in a chain cover provided to the side of the engine and an oil jet is disposed in the oil channel. Therefore, the structure of the chain cover is made more complicated, manufacturing steps are increased, added labor is required, and other disadvantageous factors are incurred.
In view of the above, there is a need to simplify the lubrication structure of the valve-operating chain used in the main gallery, which is the main oil pathway disposed in an engine.